1. Field of the Invention
The present invention relates to an annular hole cutter.
2. Description of the Related Art
An annular hole cutter disclosed in Japanese Patent No. 51-27511 has a plurality of circumferentially spaced teeth on a ring-shaped transverse cross-section at its lower end, and each of the teeth is formed with a plurality of cutting edges. A chip formed by each cutting edge is divided into narrow pieces in the direction of the width of the chip and ejected through a single flute.
In such a conventional annular hole cutter, since two to four chips cut by one tooth are ejected through a single flute, even if a chip is divided into strips in cutting, the strips join in the flute when ejected. Therefore, the cut strips interfere with one another and are formed into powders, thereby stopping the flute up. As a result, the powders are fixed and adhered to the leading edge and/or the outer periphery of the cutter, and sometimes make cutting impossible. Therefore, it is necessary to perform cutting while preventing the cut powders from being fixed to the cutter by reducing the cutting velocity.
As described above, this kind of annular hole cutter has difficulties in efficiently ejecting chips cut by cutting edges with the increased cutting velocity.